– Double Check issue, then confirm it, please do not put double effort.
– Try to show your clear logic, find solid evidence.
– Told the end user what you have done, what you gonna do and why.
– Set the right expectation for users if you cannot find root cause. This is very important under such scenario: Issue happened only once or randomly.
– Show best experience and guide users.
– Please do not make any conclusion which you are not sure.

最后，所有的这些都是建立在扎实的技术功底至上的，如果技术不扎实，用户同样也会丧失信心，举一个最简单的例子，总不能任何时候当客户问你问题的时候你都说：I am not sure about that.